The invention relates to a feed apparatus for bar stock and is particularly adapted for use with metal working machines such as lathes wherein stock is fed through the rear of the spindle to the collect or chuck.
Specifically, the invention relates to a pneumatically operated bar feed wherein the bar stock is advanced through the rotating spindle by a plunger slideably received in a feed tube. The feed tube is connected to a supply of air under pressure which is admitted to the interior of the tube at a position behind the plunger. A pair of standards are provided to support the feed tube in alignment with the particular machine tool being fed.
One of the problems with bar feed apparatus of this tybe concerns controlling the supply of pneumatic pressure to the plunger when the feed tube is not properly aligned with the machine tool. If this were to occur, the bar stock would be ejected from the feed tube with the possibility of injury to the operator or damage to the machinery. U.S. Pat. No. 3,074,566 to MacBlane, owned by the assignee herein, discloses apparatus for overcoming this problem. It comprises a locking screw which opens the air supply valve only when the feed tube is clamped in the feed position. Other examples of prior art solutions to the problem include:
U.s. pat. No. 2,300,457 PA1 U.s. pat. No. 2,272,720 PA1 U.s. pat. No. 2,327,916 PA1 U.s. pat. No. 2,339,712 PA1 U.s. pat. No. 2,892,243 PA1 U.s. pat. No. 2,334,272
In each of these examples, the supply of pneumatic pressure to the feed tube is interrupted when the locking mechanism is moved to its unlocked position. With this arrangement, deactivation of the pneumatic supply depends on the locking mechanism alone rather than on the position of the feed tube. Since the danger of premature ejection arises when the feed tube is out of position, a much more direct and reliable means for interrupting the supply of pneumatic pressure to the plunger is to directly sense the presence or absence of the feed tube itself from the aligned position. Thus, interruption of the pneumatic pressure can operate independently from the locking mechanism so that if it is accidentally thrown to its locked position with the feed tube not in place, the feed tube will not be pressurized. Furthermore, this additional safety valve will operate effectively regardless of the feed tube diameter.
A further problem with many of the prior art feed apparatus is the noise and vibration which accompanies pneumatically operated devices. This is especially a problem in bar feeds where concentric tubes are employed to supply the working fluid to the plunger because of the tendency for the tubes to vibrate and strike each other as the stock is rotated.